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## 牛客上过了，poj哇了，不知道哪里卡了

Posted by Fadeeye at 2020-07-31 17:31:27 on Problem 3417
```#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <iomanip>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <vector>
// #include <bits/stdc++.h>
#define fastio ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define sp ' '
#define endl '\n'
#define FOR(i,a,b) for( int i = a;i <= b;++i)
#define bug cout<<"--------------"<<endl
#define P pair<int, int>
#define fi first
#define se second
#define pb(x) push_back(x)
#define ppb() pop_back()
#define mp(a,b) make_pair(a,b)
#define ms(v,x) memset(v,x,sizeof(v))
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define repd(i,a,b) for(int i=a;i>=b;i--)
#define sca3(a,b,c) scanf("%d %d %d",&(a),&(b),&(c))
#define sca2(a,b) scanf("%d %d",&(a),&(b))
#define sca(a) scanf("%d",&(a));
#define sca3ll(a,b,c) scanf("%lld %lld %lld",&(a),&(b),&(c))
#define sca2ll(a,b) scanf("%lld %lld",&(a),&(b))
#define scall(a) scanf("%lld",&(a));

using namespace std;
typedef long long ll;
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
ll powmod(ll a, ll b, ll mod){ll sum = 1;while (b) {if (b & 1) {sum = (sum * a) % mod;b--;}b /= 2;a = a * a % mod;}return sum;}

const double Pi = acos(-1.0);
const double epsilon = Pi/180.0;
const int maxn = 7e5+10;
int tot = 0;
{
}
ver[++tot] = y;
//edge[tot] = z;
}
int k,n,m;
ll d[maxn],f[maxn][30],vis[maxn],cf[maxn];
ll sum[maxn];

void bfs(){
queue<int> que;
que.push(1);
d[1] = 1;
while(!que.empty()){
int x = que.front();
que.pop();
for(int i = head[x]; i; i = nexts[i]){
int y = ver[i];
if(d[y]) continue;
//dist[y] = dist[x] + edge[i];
d[y] = d[x] + 1;
f[y][0] = x;
for(int j = 1; j <= k;j++){
f[y][j] = f[f[y][j-1]][j-1];
}
que.push(y);
}
}
}
int lca(int x, int y){
if(d[x] > d[y]) swap(x,y);   //设y比较深，深度d大
for(int i = k;i >= 0;i--){
if(d[f[y][i]] >= d[x]) y = f[y][i];
}
if(x == y) return x;
for(int i = k;i >= 0;i--){
if(f[x][i] != f[y][i]){
x = f[x][i];
y = f[y][i];
}
}
return f[x][0];
}
ll dfs(int x)
{
ll cnt = 0;
for(int i = head[x];i;i = nexts[i]){
int y = ver[i];
if(vis[y] == 1) continue;
vis[y] = 1;
cnt +=  dfs(y);
}
return sum[x] = cnt+cf[x];
}
int main()
{
//freopen("input.txt", "r", stdin);
sca2(n,m);
//cin>>n>>m;
rep(i,1,n-1){
int x,y;
sca2(x,y);
//cin>>x>>y;
}
k = (int)(log(n) / log(2)) + 1;
bfs();
rep(i,1,m){
int x,y;
sca2(x,y);
cf[x]++;
cf[y]++;
cf[lca(x,y)] -= 2;
}
vis[1] = 1;
dfs(1);
ll ans = 0;
rep(i,2,n){
if(sum[i] == 0) ans += m;
else if(sum[i] == 1) ans ++;
}
printf("%lld\n",ans );
//cout<<ans<<endl;
}```

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